Assessment of cognitive functions before and after stereotactic interstitial radiosurgery of hypothalamic hamartomas in patients with gelastic seizures

Stereotactic radiosurgery as the initial management option for small-volume hypothalamic hamartomas with intractable epilepsy: a 35-year institutional experience and systematic review

OBJECTIVE

Young patients with hypothalamic hamartomas (HHs) often present with intractable epilepsy. Currently there are no established management guidelines for HH. The authors retrospectively reviewed their single-institution experience to delineate the role of stereotactic radiosurgery (SRS).

METHODS

Seven patients with HHs (4 females; median age 13.7 years, range 2.5-25 years) with no prior resection underwent SRS between 1987 and 2022. The clinical history, epilepsy profile, radiographic findings, and neurological outcomes were characterized. HH topographical types were classified according to the Régis classification. Outcome measures included Engel seizure classification, HH response, and the need for additional surgical interventions.

RESULTS

All patients had Engel class IV epilepsy. A Leksell Gamma Knife was used to deliver a median margin dose of 18 Gy (range 16-20 Gy) to a median hamartoma volume of 0.37 cm3 (range 0.20-0.89 cm3). Seizure reduction was confirmed in 6 patients, and 2 patients had regression of their hamartoma. Two patients underwent resection and/or laser interstitial thermal therapy after SRS. At follow-up, 1 patient was seizure free, 4 patients achieved Engel class II, 1 patient had Engel class III, and 1 patient had Engel class IV seizure outcomes.

CONCLUSIONS

SRS as the initial management option for HH was associated with a low risk of adverse effects. In this institutional series reviewing small-volume HHs treated with SRS, no adverse radiation effect was detected, and the majority of patients experienced seizure reduction. SRS should be considered as the first-line treatment for seizure control in patients with small-volume HHs.

Memory outcome one year after stereotactic interstitial radiosurgery in patients with epilepsy due to hypothalamic hamartomas

Epileptic seizures caused by hypothalamic hamartomas (HHs) are highly pharmacoresistant. Resective surgical approaches have shown some efficacy in controlling seizures; however, they bear a significant risk of postoperative mnemonic deterioration due to the close anatomical proximity of the HHs to structures essential for memory functions. We report on cognitive outcome in 26 patients with structural epilepsy due to HHs one year after interstitial radiosurgery. Individually, deteriorations occurred more frequently in declarative memory functions (in 20 to 50% of the patients), whereas more than 80% of the patients revealed stable or even improved performance in attentional functions. Preoperative better memory functions were associated with higher risk of postoperative performance decline. After radiosurgery, half of the patients showed more than 50%, and some up to 90%, of seizure reduction. Hypothalamic hamartoma volumes were significantly reduced at follow-up. Transient radiogenic edema found in 10/26 patients was not associated with further cognitive decline after radiosurgery. These results are highly relevant for therapeutic decisions and patient consultation on timing and choice of nonmedical treatment options for HHs.

Surgical management of hypothalamic hamartomas in patients with gelastic epilepsy

Gelastic epilepsy (GE) associated with hypothalamic hamartomas (HHs) is now a well-characterized clinical syndrome consisting of gelastic seizures starting in infancy, medically refractory seizures with or without the development of multiple seizure types, and behavioral and cognitive decline. It has been postulated that the development of the HH-GE syndrome is a result of a progressive epileptic encephalopathy or secondary epileptogenesis, which is potentially reversible with treatment of the HH. A variety of surgical options for the treatment of HHs exist, including open and endoscopic procedures, radiosurgery, interstitial radiotherapy, and stereotactic radiofrequency thermocoagulation. Surgical treatment can result in seizure freedom in up to 50% of patients and can be accompanied by significant improvements in behavior, cognition, and quality of life. Partial treatment of HHs may be sufficient to reduce seizure frequency and improve behavior and quality of life with less risk. A component of reversible cognitive dysfunction may be present in some patients with an HH-GE syndrome.

Gelastic seizures associated with hypothalamic hamartomas. An update in the clinical presentation, diagnosis and treatment

Gelastic seizures are epileptic events characterized by bouts of laughter. Laughter-like vocalization is usually combined with facial contraction in the form of a smile. Autonomic features such as flushing, tachycardia, and altered respiration are widely recognized. Conscious state may not be impaired, although this is often difficult to asses particularly in young children. Gelastic seizures have been associated classically to hypothalamic hamartomas, although different extrahypothalamic localizations have been described. Hypothalamic hamartomas are rare congenital lesions presenting with the classic triad of gelastic epilepsy, precocious puberty and developmental delay. The clinical course of patients with gelastic seizures associated with hypothalamic hamartomas is progressive, commencing with gelastic seizures in infancy, deteriorating into more complex seizure disorder resulting in intractable epilepsy. Electrophysiological, radiological, and pathophysiological studies have confirmed the intrinsic epileptogenicity of the hypothalamic hamartoma. Currently the most effective surgical approach is the trancallosal anterior interforniceal approach, however newer approaches including the endoscopic and other treatment such as radiosurgery and gamma knife have been used with success. This review focuses on the syndrome of gelastic seizures associated with hypothalamic hamartomas, but it also reviews other concepts such as status gelasticus and some aspects of gelastic seizures in other locations.

GABA(A) receptor-mediated excitation in dissociated neurons from human hypothalamic hamartomas

The cellular mechanisms underlying intrinsic epileptogenesis in human hypothalamic hamartoma (HH) are unknown. We previously reported that HH tissue is composed predominantly of GABAergic neurons, but how GABAergic-neuron-rich HH tissue is intrinsically epileptogenic is unclear. Here, we tested the hypotheses that some HH neurons exhibit immature features and that GABA excites these neurons via activation of GABA(A) receptors (GABA(A)Rs). Gramicidin-perforated and cell-attached patch-clamp recordings were performed using freshly-dissociated HH neurons to evaluate GABA(A)R-mediated currents, Cl(-) equilibrium potentials, and intracellular Cl(-) concentrations. Single-cell RT-PCR and immunocytochemical techniques were used to examine cation-Cl(-) co-transporter (NKCC1 and KCC2) gene and KCC2 protein expression and molecular markers of maturation. From a total of 93 acutely-dissociated HH neurons from 34 patients, 76% were small (soma: 6-9 microm) and 24% were large (soma: >20 microm) in size. Under gramicidin-perforated patch recording conditions, GABA(A)R activation depolarized/excited large but hyperpolarized/inhibited small HH neurons in most cases. Compared to small HH neurons, large HH neurons exhibited more positive Cl(-) equilibrium potentials, higher intracellular Cl(-) concentrations, lower KCC2 expression, and an immature phenotype, consistent with GABA(A)R-mediated excitation. Taken collectively, we provide novel evidence for and mechanistic insights into HH epileptogenicity: GABA(A)R-mediated excitation.

Radiosurgery for hypothalamic hamartomas

Radiosurgery plays an important role in the treatment of refractory seizures induced by hypothalamic hamartomas (HHs). These lesions, deeply located and surrounded by a delicate vascular and neuronal network, are often associated with catastrophic epilepsy leading to progressive cognitive and behavioral deterioration. Surgical approaches include microsurgical resection, endoscopic resection or disconnection, radiofrequency lesioning, and interstitial brachytherapy. Radiosurgery is an emerging treatment modality for HHs, which provides excellent seizure outcomes and no lasting complications to date.

Treatment options for gelastic epilepsy due to hypothalamic hamartoma: interstitial radiosurgery

Surgical treatment of hypothalamic hamartomas (HHs) as the underlying etiology of gelastic epilepsy is associated with a high risk of complications because of the close vicinity of adjacent structures such as the optic tracts and mammillary bodies. Treatment with interstitial radiosurgery uses stereotactically implanted (125)I seeds emitting gamma radiation from the center of the lesion, with a steep spatial gradient, over a period of about 3 weeks. This form of HH therapy offers particular advantages regarding the risk for major side effects. In a series of 15 children and adolescents treated in Freiburg, Germany, 53% of patients achieved significant improvement in seizure frequency (Engel class I or II outcome). Transient side effects were related to the development of local edema, resulting in headache and mental slowing. A persistent weight gain was noted in 3 patients, which was severe in 1 (20 kg). There were no other neurologic, neuropsychologic, or neuropsychiatric side effects, which compares favorably with most surgical series.